Animals Convert Amino Nitrogen To Varied End Products

Different animals excrete excess nitrogen as ammonia, uric acid, or urea. The aqueous environment of teleostean fish, which are ammonotelic (excrete ammonia), compels them to excrete water continuously, facilitating excretion of highly toxic ammonia. Birds, which must conserve water and maintain low weight, are uri-cotelic and excrete uric acid as semisolid guano. Many


1. UB — C — O- + E,— SH + ATP-*- AMP + PP; + UB — C — S — E,


2. UB — C — S — E, + E2 — SH-*- E, — SH + UB — C — S — E2



3. UB — C — S — E2 + H2N — £ — Protein-E2 — SH + UB — C — N — £ — Protein

Figure 29-1. Partial reactions in the attachment of ubiquitin (UB) to proteins. (1) The terminal COOH of ubiquitin forms a thioester bond with an -SH of E1 in a reaction driven by conversion of ATP to AMP and PP,. Subsequent hydrolysis of PP| by pyrophosphatase ensures that reaction 1 will proceed readily. (2) A thioester exchange reaction transfers activated ubiquitin to E2. (3) E3 catalyzes transfer of ubiquitin to e-amino groups of lysyl residues of target proteins.

land animals, including humans, are ureotelic and excrete nontoxic, water-soluble urea. High blood urea levels in renal disease are a consequence—not a cause—of impaired renal function.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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